1. Field of the Invention
The present invention relates to a carrier tape on which semiconductor chips are to be mounted in a tape automated bonding (TAB) method, and also relates to a method of manufacturing a semiconductor device employing the .#carrier tape.
2. Description of the Related Art
FIGS. 7A and 7B are a plan view and a sectional view, respectively, of a part of a conventional carrier tape on which a semiconductor chip is mounted. The carrier tape has a film 1 formed of an insulating material such as polyimide. The film 1 has a plurality of perforations 6 formed at equal intervals along the edges of the film, and a rectangular center device hole 3 formed centrally between the edges of the film for receiving a semiconductor chip 2. A plurality of outer lead holes 5 are formed at the periphery of the center device hole 3. A plurality of leads 4 formed of copper are secured to the surface of the film 1. These leads 4 are supported by a lead supporting portion 7 positioned between the center device hole 3 and the outer lead holes 5. A front end portion of each lead 4 projects into the center device hole 3 as an inner lead 4a, while an intermediate portion of the lead 4 is positioned above the corresponding outer lead hole 5 as an outer lead 4b which is to be connected to an external circuit. A test pad 4c is formed at the rear end of each lead 4. The lead supporting portion 7 is linked to portions of the film 1 by bridge portions 8 each positioned between two adjacent outer lead holes 5.
As shown in FIG. 7B, within the center device hole 3 of the carrier tape, the inner lead 4a of each lead 4 is connected to a bump electrode 21 of the semiconductor chip 2. The semiconductor chip 2 and the associated part of the carrier tape constitute a tape carrier.
Such a tape carrier is sealed with a resin package, in order to protect the semiconductor chip 2, the leads 4, etc. from external forces and the external environment. The resin package is molded using, for instance, an upper mold part 10a and a lower mold part 10b, shown in FIG. 8. During resin molding, the tape carrier is set between the upper mold part 10a and the lower mold part 10b. At this time, the tape carrier is aligned in such a manner that the semiconductor chip 2 is received in a cavity half 12b of the lower mold part 10b. Thereafter, the upper mold part 10a and the lower mold part 10b are clamped, and a molten resin 11 is injected into a cavity defined by a cavity half 12a of the upper mold part 10a and the cavity half 12b of the lower mold part 10b, through a groove-shaped gate 13 and a gate land 13a formed in the upper mold part 10a. After the curing of the resin 11, a molded product, such as that shown in FIG. 9, is obtained. After the molded product has been taken out from the upper and lower mold parts 10a and 10b, the so-called gate-breaking process is executed. In this process, the molded resin 11 is broken at a portion 11a corresponding to the gate land 13a of the upper mold part 10a, thereby removing an unnecessary, gate-corresponding resin portion 11b. Furthermore, each of the leads 4 is cut along the boundary between the outer lead 4b and the test pad 4c, and each of the bridge portions 8 of the film 1 is cut off, thereby obtaining a semiconductor device.
The above described art, however, involves the following problems. Since the groove-shaped gate 13 of the upper mold part 10a is positioned above lead hole 5a, one of the outer lead holes 5 of the film 1, as shown in FIG. 8, during resin molding, molten resin 11 which is to be injected into the cavity flows through the gate 13 in the direction indicated by an arrow A in FIG. 7A. As a result, the resin 11 enters not only the cavity but also the outer lead hole 5a of the film 1, whereby an unnecessary molded resin portion 11c, disposed partially within the land-corresponding resin portion 11a, is formed, as shown in FIG. 9. Accordingly, it is necessary to perform, after the resin molding process, the process of removing an unnecessary molded resin portion 11c, thereby inevitably complicating the manufacture of the semiconductor device.
In addition, since the leads 4 generally have a relatively small thickness of about 35 .mu.m, the outer leads 4b tend to be broken when the unnecessary molded resin portion 11c is being removed. If the leads break the semiconductor device is unreliable.
Furthermore, when, with a view to rendering the entire structure of a semiconductor device thin, the thickness of that resin portion over the semiconductor chip 2 is reduced, as shown in FIG. 9, the thickness t2 the molded resin 11 on the lead supporting portion 7 of the film 1 becomes relatively thin compared with the thickness t1 of the resin portion 11a corresponding to the gate land 13a of the upper mold part 10a. Accordingly, there is a risk that a package-forming portion of the molded resin 11 may chip during the gate-breaking process, thereby opening the package and leading to a degradation in the qualities of the semiconductor device.